The present invention relates to a plasma processing method and apparatus, particularly to a plasma processing method and apparatus using a microplasma source, and more particularly to a plasma processing apparatus and method to be applied to the manufacturing processes of electronic devices such as semiconductors and MEMS (Micro Electromechanical Systems).
In general, a resist process is used when an object to be processed represented by a substrate on the surface of which a thin film is formed is subjected to a patterning process. FIGS. 23A through 23D show examples thereof. Referring to FIGS. 23A through 23D, first of all, a photoresist 27 is coated on the surface of an object 26 to be processed (see FIG. 23A). Next, if the photoresist 27 is exposed to light by means of an exposure apparatus and thereafter developed, then either of the exposed portion or the non-exposed portion of the photoresist 27 is removed, allowing the photoresist 27 to be patterned into the desired shape (see FIG. 23B). Subsequently, if the object 26 is placed in a vacuum vessel and plasma is generated inside the vacuum vessel to subject the object 26 to an etching process with the resist 27 used as a mask, then the surface of the object 26 is patterned into the desired shape (see FIG. 23C). Finally, by removing the resist 27 with oxygen plasma, an organic solvent, or the like, the processing is completed (see FIG. 23D).
The above-mentioned resist process, which has been appropriate for accurately forming a fine pattern, has therefore come to play an important role in manufacturing electronic devices such as semiconductors. However, there is a defect that the process is complicated.
Accordingly, there is currently being examined a new processing method that uses no resist process. As one example thereof, FIGS. 24-25 show perspective views of a processing apparatus provided with a microplasma source employed in a prior art example. FIG. 25 shows a sectional view cut in the plane A of FIG. 24. Referring to FIGS. 24 and 25, a space 73 (dot-hatching portion of FIG. 25, hereinafter referred to as a plasma space 73) for generating microplasma is formed between two ceramic plates 71 and 72. Side portions of the ceramic plates 71 and 72 are bonded to ceramic bars 74, 75, and 76. Gas is supplied from a gas supply unit 77 to the plasma space 73 via a pipe 78 and the ceramic bar 76. A through hole that serves as a gas supply inlet is provided at the ceramic bar 76 and joined to the pipe 78. By arranging an opening 80 of the microplasma source in the vicinity of a substrate 81 that serves as an object to be processed, supplying high-frequency power of 13.56 MHz from a high-frequency power supply 82 to a high-frequency electrode 83 while supplying gas to the plasma space 73 and grounding a grounding electrode 84, plasma is generated in the plasma space 73 to make activated particles emitted from the opening 80 of the microplasma source act on the substrate 81, allowing a fine linear portion 85 to be processed on the surface of the substrate 81. It is to be noted that the high-frequency electrode 83 and the grounding electrode 84 are parallel plate electrodes provided with interposition of the plasma space 73. The width B of the opening 80 of the microplasma source is 1 mm, and the distance C between the opening 80 of the microplasma source and the substrate 81 is 0.1 mm.
For example, on the condition that He is supplied by 2000 sccm and CF4 is supplied by 4 sccm as gas and high-frequency power of 30 W is supplied, a molybdenum thin film formed on the substrate 81 can be subjected to an etching process.
However, in the processing described in connection with the prior art example, the active species dissociated by the plasma effuse along the surface of the substrate 81 as indicated by arrows in FIG. 25, and this has therefore led to an issue that the processing has been disadvantageously effected beyond the desired fine linear portion. FIG. 26 shows the obtained etching profile. In this case, on the assumption that the depth of the portion most deeply etched was D and the width of the portion shallower by D×0.8 than the bottom of the pattern was a processing width E, then E was 3.1 mm. Since the width B of the opening 10 of the microplasma source was 1 mm, then the processing width E disadvantageously became three or more times the width.
The present invention is accomplished in view of the aforementioned conventional issues and has the object of providing a plasma processing method and apparatus for accurately forming the desired fine linear portion by plasma processing.